1. Field of the Invention
The systems and methods of this invention generally relate to communication systems. In particular, the systems and methods of this invention relate to asynchronous transfer mode (ATM) over digital subscriber line (DSL).
2. Description of Related Art
FIG. 1 illustrates the conventional configuration of a system for transporting ATM over DSL using a single latency ADSL configuration. As of the time of filing, single latency is most common form of ADSL deployment. Further details of this specific architecture can be found in DSL Forum Recommendation TR-042, incorporated herein by reference in its entirety.
For the system illustrated in FIG. 1, the access node 10 serves as an ATM layer multiplexer/concentrator between the ATM core network 2 and the access network. As described in the above referenced DSL Forum Recommendation, for ATM systems, the channelization of different payloads is embedded within the ATM data stream using different virtual paths (VP) and/or virtual channels (VC). In the downstream direction, the VP/VC Mux module 16 and VPI/VCI translation module 14 receive cells from the core network interface element 12 and function to perform cell routing based on a virtual path identifier (VPI) and/or virtual channel identifier (VCI) to the appropriate ATU-C 18. In the upstream direction, the VP/VC Mux module 16 and the VPI/VCI translation module 14 function to combine the cell streams from the ATU-C's 18 into a single ATM cell stream to the core ATM network 2.
The broadband network termination (B-NT) 100 performs the functions of terminating the ADSL signal entering the user's premises via the twisted pair cable and the ATU-R 22 and provides either the T, S or R interface towards the premises distribution network/terminal equipment 4. The access ATM module 26 and the VP/VC Mux module 24 perform the ATM layer functions to support the TC layers in the ATU-R. The broadband network termination 100 may also contain VPI/VCI translation functions to support multiplex/demuliplex of VC's between the ATU-R 22 and the premise distribution network/terminal equipment 4 on a VPI and/or VCI bases. The broadband network termination 100 may also comprise a PDN/TE interface element 28 and SAR module 30 the functions of which are well known and will be omitted for sake of clarity.